The invention relates to coupled hose assemblies, but more particularly, the invention relates to an improved seal between a metallic coupling and a polymeric hose.
Metallic couplings typically have a male stem portion that is insertable into a hose bore and a ferrule portion that is concentric with the male stem portion. Together, the male stem and ferrule portions define an annular cavity for receiving a hose end. The coupling is retained by pinching part of a hose end between the ferrule and stem portions. Pinching is accomplished either by radially reducing the size of the ferrule, or by radially increasing the size of the male stem. In some applications, the ferrule may be attached to the stem by means of interlocking collars.
The problem to be reckoned with in all liquid transfer type hose assemblies is that of forming a liquid tight seal between a coupling and hose at expected operating temperature, pressure, and hose flexing conditions. Sealing is typically accomplished by pressing the bore of a hose against a stem, which may include a plurality of circumferential serrations. The elastomeric characteristics of a hose polymer are relied on to maintain pressure between the hose bore and stem as the hose is pinched between the ferrule and stem. While the resiliency of the hose and the pinched area may be sufficient to maintain pressure to effect sealing between the hose and coupling in most environments, problems can sometimes occur at low operating temperatures after the hose becomes "compression set" where it is pinched. Once "compression set", the hose has a rate of thermal contraction that is greater than that of the metallic coupling making the hose susceptible to "cold leaking" at the low temperatures of its expected operating environment as, for example, a temperature range of about 135.degree. C. to about -40.degree. C.